Sleep disordered breathing and nocturnal polyuria: nocturia and enuresis

Although nocturnal voiding is frequently attributed to urologic disorders, nocturia and enuresis are also important symptoms of sleep-disordered breathing. However, polyuria can be elicited by obstructive sleep apnea as well as bedrest, microgravity and other experimental conditions where the blood volume is shifted centrally to the upper body. The nocturnal polyuria of sleep apnea is an evoked response to conditions of negative intrathoracic pressure due to inspiratory effort posed against a closed airway. The mechanism for this natriuretic response is the release of atrial natriuretic peptide due to cardiac distension caused by the negative pressure environment. This cardiac hormone increases sodium and water excretion and also inhibits other hormone systems that regulate fluid volume, vasopressin and the rennin-angiotensin-aldosterone complex. Treatment of sleep apnea and airway compromise has been shown to reverse nocturnal polyuria and thereby reduce or eliminate nocturia and enuresis. Thus, careful evaluation of nocturia and enuresis for evidence of nocturnal polyuria can increase the diagnostic certainty of referring primary care providers and sleep specialists. In addition, the resolution of these bothersome symptoms after treatment can contribute to patient satisfaction as well as reinforce treatment compliance.